While the world is still doing the best to figure out just what buzz.google.com actually does, we do know the following:

• It works with gmail (Google's free email service)
• It allows you to post your emails and it's contents a recipient, group of recipients or the general public
• It allows you to tag in content into your messaging fromt the web
• Pushes YouTube video and flickr respectively as it's delivery medium of choice (IMHO, the best at least today)
• Comments to posts are then sent to your inbox, much like email replies
• Social integration with Twitter, Picasa and more
• Google buzz makes recommendations on content popularity and I'm assuming profiling criteria based on what it finds in your gmail account and posts

Smart phone integration:

Related Mashable.com articles on Google buzz:

• Google Buzz: What It Means for Twitter and Facebook
• What Google Buzz Means for Mobile
• Google Buzz: Competitors and Experts React
• Google Buzz: Will You Use It?
• The Location Implications of Google Buzz